SEATTLE – Drivers have a little more than two weeks left to make plans for a four-day closure of State Route 99 in Seattle. The upcoming closure is expected to cause backups on city streets and increase delays on Interstate 5.

Both directions of SR 99 will close between South Spokane Street and Valley Street from 10 p.m. Friday, Aug. 22, to 5 a.m. Monday, Aug. 25. The section of SR 99 between Spokane Street and the south end of the Battery Street Tunnel will reopen just before the Monday morning commute, but the highway will remain closed through the tunnel to Valley Street until 5 a.m. Wednesday, Aug. 27.

The Washington State Department of Transportation will need help from drivers to keep traffic moving.

“Experience has shown that weekday closures on SR 99 have a spillover effect onto other north-south routes into downtown Seattle,” said WSDOT Deputy Administrator Dave Sowers. “We will see long delays and big backups if drivers don’t plan ahead, travel during non-peak commute times, and leave plenty of time to get to their destinations.”

Contractor crews working for WSDOT will use the four-day closure to demolish (pdf 5 mb) an existing bridge and rebuild a roadway on the section of SR 99 that crosses above the now-closed Broad Street. This new section of highway will become part of the permanent connection between the SR 99 tunnel’s north portal and Aurora Avenue North.

Other important work will take place during the closure. Over the weekend of Aug. 23 and 24, crews will replace 81 damaged or cracked pieces of concrete road panels that make up the SR 99 lanes between South Spokane and South Holgate streets, as well as repair an expansion joint at the northbound SR 99 exit to Seneca Street. During the entire four day closure, contractor crews will also reroute major utility lines from underneath SR 99 near Harrison Street.

Closure details

At 10 p.m. Friday, Aug. 22, crews will close both directions of SR 99 between South Spokane Street and Valley Street. Northbound SR 99 will be open from South Royal Brougham Way until midnight Friday, Aug. 22 for exiting Seahawks traffic.

At 5 a.m. Monday, Aug. 25, crews will reopen both directions of SR 99 south of the Battery Street Tunnel. Both directions of SR 99 will remain closed between the south end of the Battery Street Tunnel and Valley Street.

At 5 a.m. Wednesday, Aug. 27, crews will reopen both directions of SR 99 between the south end of the Battery Street Tunnel and Valley Street.

Know before you goDuring this critical work, WSDOT encourages drivers to allow plenty of extra time and expect additional congestion on alternate routes including I-5 and surface streets. Drivers should leave early or delay trips to avoid traveling during the peak commute periods, and consider alternative travel modes such as King County Metro, sharing a ride in a car or vanpool, walking or riding a bicycle. WSDOT also has a number of ways to help travelers stay informed during the closure.